So many factors play into a situation like this. Many illnesses make a person uncomfortable when they eat. Some actually impact the sense of taste. Some create a depression that makes eating a chore.

If you are preparing foods for her and she is just not eating, you might try fixing her favorite foods! If you don't know what she might like, ask her if she could eat anything what would it be? Most of us have foods that bring us happy thoughts of past good times. When my mother in law was gravely ill, we could get some spark back if we presented her things that we knew were her guilty pleasures. Such as Fresh Garden Ripened tomatoes with a sprinkle of salt. We actually had to feed them to her. But she would open her mouth for a bit and you could see her savor the experience. After the first bite she became like an infant and would open her mouth for more. Fresh Strawberries were another of her favorites.

The idea is to awaken the senses. If she is not eating, that is probably more dangerous to her health than eating a little something that might be considered unhealthy.

So many possible factors, including losing the ability to smell/taste. Also, just not experiencing hunger. Ask if she notices any change in taste or hunger. Also, do her teeth hurt? Soup could be a great help. Could you make a shake or smoothie that would be soothing and nutritious?